Diffusion transfer photographic processes and elements utilizing ph-sensitive agents to prevent fogging by extraneous actinic radiation during development

ABSTRACT

THIS INVENTION RELATES TO PHOTOGRAPHY, AND MORE PARTICULARLY, IT RELATES TO THE USE OF CERTAIN INDICATOR DYES DERIVED FROM INDOLES AS OPTICAL FILTER AGENTS TO PROTECT A SELECTIVELY EXPOSED PHOTOSENSITIVE MATERIAL FROM POSTEXPOSURE FOGGING IN PHOTOGRAPHIC PROCESSES WHERE DEVELOPMENT OF THE PHOTOSENSITIVE MATERIAL IS CONDUCTED IN THE PRESENCE OF EXTRANEOUS INCIDENT LIGHT. THESE INDICATOR DYES CONTAIN AN INDOLE RADICAL, A SECOND AROMATIC RADICAL AND A RING-CLOSING MOIETY BONDED TO THE AROMATIC RADICAL AND TO THE 2- OR 3-POSITION OF THE INDOLE RADICAL. AT A FIRST PH THEY HAVE A HIGHLY COLORED, LIGHT-ABSORBING FORM CAPABLE OF ABSORBING RADIATION WITHIN A PREDETERMINED WAVELENGTH RANGE IS THE SHORTER WAVELENGTH REGION OF THE VISIBLE SPECTRUM AND AT A SECOND PH HAVE A COLORLESS FORM THAT IS SUBSTANTIALLY NON-LIGHT-ABSORBING IN THE VISIBLE   SPECTRUM. BY SELECTING A DYE FROM THIS CLASS WHICH IS IN ITS LIGHT-ABSORBING FORM AT THE PH AT WHICH DEVELOPMENT IS PERFORMED, PROTECTION OF THE EXPOSED PHOTOSENSITIVE MATERIAL FROM RADIATION ACTINIC THERETO IS AFFORDED WITHIN THE WAVELENGTH RANGE ABSORBED BY THE DYE AND SUBSEQUENT TO AT LEAST THE INITIAL STAGES OF DEVELOPMENT, THE DYE MAY BE RENDERED SUBSTANTIALLY COLORLESS BY ADJUSTING THE PH TO PERMIT VIEWING OF THE FINAL IMAGE.

Nov. 7, 1972 5, BLOOM ETAL 3,702,244

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS IUTILIZING [AH-SENSITIVE AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet l INVENTORS STANLEY M. BLOOM ALAN L. BORROR BY PAUL S. HUYFFER PAUL T. MACGREGOR blww n and M' ATTORNEYS Nov. 7, 172

S. M. BLOOM ETAL DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING H-SENSITIVE AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21, 1971 15 Sheets-Sheet 2 m w m NOV. 7, 19'22 s, BLQQM ETAL. 3,762,244

DIFFUSION TRANSFER PHOTOGRAPHIG PROCESSES AND ELEMENTs UTILIZING H-SENSITIVE AGENTS To PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 l5 Sheets-Sheet 3 INVENTORS STANLEY M. BLQOM ALAN L. HORROR BY PAUL S. HUYFFER PAUL T. MACGREGOR fi/wwoz Mm AT TORNE Y5 NOV. 7, 1972 s, BLOOM ETAL 3,702,4

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet 4.

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INVENTORS STANLEY M. BLOOM ALAN L. BORROR BY PAUL S HUYFFER PAUL T. MACGREGOR 25W 01nd m ATTORNFYQ NOV. 7, 1972 s, BLOOM El'AL 3,72,44

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING IX-SENSITIVE AGENTS TO PREVENT FOGGING BY.

EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet 5 Q 2% 8 E 2 .J i E 0% g I (9 o 5 a 4 a O -.m Q

f .3 a A A m, g 3 E 9 O' o o o 1 as 901 wsuau NOISSIWSNVHJ. 'WOLLdO V INVENTORS I STANLEY M. BLOOM ALAN BORROR BY PAUL s. HUYFFER PAUL T. MACGREGOR fi/zoawn and m ATTORNEYS NOV. 7, 1972 5, BLOOM ETAL 3,792,244

ND ELEMENTS DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES A UTILIZING H-SENSITIVE AGENTS TO PREVENT FOGGING BY EXTRANEOUS AGTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet 6 m o; m mzomozzjaz z. 1525MB; ommwm om 0 0mm 00m 0mm com 0? 00 0mm mmmmm 1 mm si NLL MMUU AM no 0 ..9 r O... 1 v: o 1 l H. V N s m S & o m o N -md m N B o u m o m 9 s 0 V m o Q. Tod

3W mm ATTORNEYS NOV. 7, 1972 s, BLOOM ETAL 3,7QZZ44 DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING H-sENsITIvE AGENTS To PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet '1 I I Q m qn N O I (\i O O O O O (BTV'OS 90'!) ALISNBCI NOISSIWSNVtLL 'IVQIldO INVENTORS STANLEY M. BLOOM ALAN L. HORROR y PAUL S. HUYFFER PAUL T. MACGREGOR /zawwa and W0,

ATTORNEYS NOV. 7, 1972 s, BLOOM ETAL 3,792,4 DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING H-sENsITIvE AGENTS To PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet 23 (B'IVOS 901) ALISNBO NOISSIWSNVHJ. "IVOIldO TORS STANLEY M. BLOOM ALAN L. BORROR BY PAUL S. HUYFFER PAUL TI MACGREGOR km and m ATTORNEYS NOV. 7, 1972 s, BLOOM EI'AL 3,702,244

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING PH-SENSITIVE AGENTS To PREVENT FOGGING BY ExTRANEoUs ACTINIG RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 v Sheets-Sheet 9 0 5 00 5 WAVELENGTH IN MILLIMICRONS F I G. I2

. I I I I I Q "I N o' O o O o l IIN NVELL 'IVOLLdO (TWOS 1) ALISNBO N0 SS 3 ORS STANLEY M. BLOOM ALAN L. BORROR BY PAUL S. HUYFFER PAUL T. MACGREGOR E/zow n a/rwl m ATTORNEYS Nov. 7, 1972 5, BLOOM ETAL 3,792,244

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE AGENTS To PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21, 1971 15 Sheets-Sheet 10 0 IO N 2 8 8 2 2 j m ..8 E '1 2 w E 0 LL. 2 8 u l m U 2 3 l l l l l I 8 L m 0 m 0 q N. 8 (\i o o o o 1 A I N30 NOISSIWSNVHJ. 'lVOLLdO (3 was 901) Is INVENTORS STANLEY M. BLOOM ALAN L. BORROR BY PAUL S. HUYFFER PAUL T. MACGREGOR UM a/rml M ATTORNEYS NOV. 7, 1972 s, BLOOM El'AL 3,7UZ,4

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING H-sENsITIvE AGENTS To PREVENT FOGGING BY ExTRANEoUs ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet 11 O T m N Q 2 8 8 2 E 8 E z :1: o E *8 D ID LU 3 0 u) I I I l I l I l m 0 ID 0 m I 8 (\i O O 0 d O IN NVHl "IVOIldO (BIVOS 90'1) ALISNBG NOISS S INVENTORS STANLEY M. BLOOM ALAN L. BORROR BY PAUL S. HUYFFER PAUL I MACGREGOR @W W m ATTORNEYS NOV. 7, 1972 s, BLOOM ETAL 3,702,244

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE AGENTS To PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 I5 Sheets-Sheet 12 l i l m I N Q Q Q (:rwas 90'!) AJJSNBCI NOISSIWSNVHJ. 'lVOLLcIO TORS STANLEY M. BLOOM ALAN L.BORROR BY PAUL S. HUYFFER PAUL 1'. MACGREGOR fi/ww n and m ATTORNEYS NOV. 7, 1972 s, BLOOM ETAL 3,702,244

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING H-SENSITIVE AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet 13 w mi . mQO

I O N (:nvos 901) ALISNBO NOISSIWSNVHI IVOlidO INVENTORS STANLEY M. BLOOM ALAN L. BORROR BY PAUL s. HUYFFER PAUL T. MACGREGOR fi mu n. (10ml. ATTORNEYS Nov. 7, 1972 s, BLOOM EI'AL 3,702,244

DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSES AND ELEMENTS UTILIZING PH-SENSITIVE AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 21. 1971 15 Sheets-Sheet 14.

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m MILLIMICRONS (BWVOS QO'I) MISNBCI NOISSIINSNVHL 'IVOLLdO lNvENTo s STANLEY M. BLOOM ALAN L. BORROR BY PAUL S. HUYFFER PAUL T MACGREGOR ATTORNEYS Nov. 7,

IATION DURING DEVELOPMENT 15 Sheets-Sheet 15 m V. MB G MN I W0 F T EN E L H E R R 0 T Mm HT OPN O w LwAm B W 0 IC um S SI NT EC SJUA MES R W m W IA I ZR IT ULX F ZFM 7 D 9 1 Filed Jan. 21. 1971 (B'IVQS 90"1) ALISNBCI NOISSIWSNVHL 'IVJLLdO INVENTORS STANLEY MBLOOM ALAN L. BORROR BY PAUL S. HUYFFER PAUL T. MACGREGOR ATTORNEYS United States Patent 3,702,244 DIFFUSION TRANSFER PHOTOGRAPHIC PROC- ESSES AND ELEMENTS UTILIZING pH-SENSI- TIVE AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Stanley M. Bloom, Waban, Alan L. Borror, Arlington,

and Paul S. Huyifer and Paul T. MacGregor, Lexington, Mass., assignors to Polaroid Corporation, Cambridge, Mass.

Filed Jan. 21, 1971, Ser. No. 108,260 Int. Cl. G03c 7/00, /54, 1/40 US. Cl. 96-3 159 Claims ABSTRACT OF THE DISCLOSURE This invention relates to photography, and more particularly, it relates to the use of certain indicator dyes derived from indoles as optical filter agents to protect a selectively exposed photosensitive material from postexposure fogging in photographic processes where development of the photosensitive material is conducted in the presence of extraneous incident light. These indicator dyes contain an indole radical, a second aromatic radical and a ring-closing moiety bonded to the aromatic radical and to the 2- or 3-position of the indole radical. At a first pH they have a highly colored, light-absorbing form capable of absorbing radiation within a predetermined wavelength range in the shorter wavelength region of the visible spectrum and at a second pH have a colorless form that is substantially non-light-absorbing in the visible spectrum. By selecting a dye from this class which is in its light-absorbing form at the pH at which development is performed, protection of the exposed photosensitive material from radiation actinic thereto is afforded within the wavelength range absorbed by the dye and subsequent to at least the initial stages of development, the dye may be rendered substantially colorless by adjusting the pH to permit viewing of the final image.

In a preferred embodiment, the indole dye or dyes are used in conjunction with a second dye or dyes having a principal absorption in at least a partially different wavelength range, and the indole dye(s) and second dye(s) together afford protection over the wavelength range of about 400 nm. to 700 nm.

BACKGROUND OF THE INVENTION (1) Field of the invention The present invention relates to photography and more particularly to photographic processes and products wherein certain light-absorbing dyes are employed as optical filter agents to protect a selectively exposed photosensitive material from further exposure by incident radiation actinic thereto during processing in the presence of light.

(2) Description of the prior art The production of both silver and color images including monochromatic and multicolor images employing diffusion transfer techniques is now well-known. In these processes, a photosensitive element comprising a layer of photosensitive material is exposed to provide a latent image therein and wetted by a liquid processing composition, for example, by immersion, coating, spraying, flowing, etc., in the dark and the exposed photosensitive ele ment superposed prior to, during or after wetting, on a sheetlike support element which may be utilized as an image-receiving element. As a function of developing the latent image, there is formed an imagewise distribution of image-forming components which imagewise distribution is transferred, by imbibition, to form the final image either in the photosensitive or image-receiving element.

US. Pat. No. 3,415,644, discloses a composite photosensitive structure, particularly adapted for use in reflection type photographic diffusion transfer color processes. This structure comprises a plurality of essential layers including, in sequence, a dimensionally stable opaque layer; one or more silver halide emulsion layers having associated therewith dye image-providing material which is soluble and diifusible, in alkali, at a first pH, as a function of the point-to-point degree of its associated silver halide emulsions exposure to incident actinic radiation; a polymeric layer adapted to receive solubilized dye image-providing material diffusing thereto; a polymeric layer containing sufiicient acidifying capacity to eifect reduction of a processing composition from the first pH to a second pH at which the dye image-providing material is substantially nondiifusible; and a dimensionally stable transparent layer. This structure may be exposed to incident actinic radiation and processed by interposing, intermediate the silver halide emulsion layer and the reception layer, an alkaline processing composition providing the first pH and containing a light-reflecting agent, for example, titanium dioxide to provide a white background. The light-reflecting agent (referred to in said patent as an opacifying agent) also performs an opacifying function, i.e., it is effective to mask the developed silver halide emulsions and also acts to protect the photoexposed emulsions from postexposure fogging by light passing through the transparent layer it the photo-exposed film unit is removed from the camera before image formation is complete.

In a preferred embodiment, the composite photosensitive structure includes a rupturable container, retaining the alkaline processing composition having the first pH and reflecting agent, fixedly positioned extending transverse a leading edge of the composite structure in order to effect, upon application of compressive pressure to the container, discharge of the processing composition intermediate the opposed surfaces of the reception layer and the next adjacent silver halide emulsion.

The liquid processing composition distributed intermediate the reception layer and the silver halide emulsion, permeates the silver halide emulsion layers of the composite photosensitive structure to initiate development of the latent images contained therein resultant from photoexposure. As a consequence of the development of the latent images, dye image-providing material associated with each of the respective silver halide emulsion layers is individually immobilized as a function of the point-topoint degree of the respective silver halide emulsion layer photoexposure, resulting in imagewise distributions of mobile dye image-providing materials adapted to transfer, by diffusion, to the reception layer to provide the desired transfer dye image. Subsequent to substantial dye image formation in the reception layer, a sufiicient portion of the ions of the alkaline processing composition transfers, by diffusion, to the polymeric neutralizing layer to effect reduction in the alkalinity of the composite film unit to the second pH at which dye image-providing material is substantially non-dilfusible, and further dye image-providing material transfer is thereby substantially obviated.

The transfer dye image is viewed, as a reflection image, through the dimensionally stable transparent layer against the background provided by the reflecting agent, distributed as a component of the processing composition, intermediate the reception layer and next adjacent silver halide emulsion layer. The thus-formed stratum efiectively masks residual dye image-providing material retained in association with the developed silver halide emulsion layer subsequent to processing.

In the copending U.S. patent application Ser. No. 786,- 352 of Edwin H. Land, filed Dec. 23, 1968, now abandoned, and copending U.S. patent application Ser. No. 101,968, filed Dec. 28, 1970 in part a continuation of Ser. No. 786,352, an organic light-absorbing reagent (or optical filter agent), such as a dye, which is present as a light-absorbing species at the first pH and which may be converted to a substantially non-light-absorbing species at the second pH is used in conjunction with the light-reflecting agent to protect the selectively exposed silver halide emulsion from post-exposure when development of the photoexposed emulsions is conducted in the presence of extraneous incident actinic radiation impinging on the transparent layer of the film unit.

In the copending U.S. patent application Ser. No. 43,782, of Edwin H. Land, filed June 5, 1970, now abandoned, the stratum interposed intermediate, the reception layer and next adjacent silver halide layer is disclosed to comprise an inorganic light-reflecting pigment dispersion containing reflecting pigment in a concentration per se insufiicient, distributed as a layer intermediate the reception layer and next adjacent silver halide layer, to effectively prevent transmission of a given level of radiation actinic to the silver halide layer therethrough and at least one optical filter agent at a pH above the pKa of the optical filter agent, in a concentration per se also insuflicient to prevent transmission of said given level of actinic radiation therethrough, which concentrations individually and additively are together insufiicient to prevent said transmission of incident actinic radiation but in admixture are synergistically effective to provide the requisite transmission density to prevent such transmission of said given level of radiation until modulation of the environmental pH to below the pKa of the optical filter agent whereby the transmission density is rendered sufliciently low to permit substantially immediate viewing of transfer image formation against the background provided by the reflecting pigment.

SUMMARY OF THE INVENTION It is the primary object of the present invention to provide photographic processes, products and compositions, employing as optical filter agents, a particular class of indicator dyes derived from indoles.

Other objects of the present invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the processes involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements of which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

According to the present invention, it has been discovered quite unexpectedly that certain dyes, namely, indicator dyes containing an indole radical, a second aromatic radical and a ring-closing moiety bonded to the aromatic radical and to the 2- or 3-position of the indole radical are eminently suitable for use as optical filter agents for protecting an exposed photosensitive material from post-exposure fogging in photographic processes where the photosensitive material subsequent to selective exposure to form a latent image therein and during at least the initial stages of developing the latent image, is non-selectively exposed to extraneous incident light. These indictaor dyes, because they contain at least one indole radical bonded through the 2- or 3-position to the ringclosing moiety, are capable of absorbing radiation wtihin a predetermined wavelength range in the shorter wavelength region of the visible spectrum. Depending upon the particular indole indicator dye selected, protection of photographic materials from post-exposure fogging may be achieved substantially throughout the blue portion of the spectrum and in the green portion as well. To achieve a highly effective light absorbing ystem throughout the visible spectrum, i.e., between about 400 nm. and 700 nm., the indole indicator dye(s) may be used in combination with another optical filter agent, such as a second dye or dyes, which are effective absorbers of radiation in the longer wavelength region of the spectrum.

Besides being efficient absorbers of short wavelength radiation, this class of dyes because they are indicators or pH sensitive dyes possess pectral absorption characteristics which are reversibly alterable in response to changes in environmental pH. These dyes possess a highly colored form capable of absorbing visible radiation at a first pH value and may be converted to a substantially colorless form, i.e., a form substantially nonabsorbing in the visible spectrum at a second pH value, and vice versa. Though these dyes may be used in any photographic process for protecting a selectively exposed photosensitive material from postexposure fogging by radiation within said wavelength range during development of a latent image to a visible image, these indole dyes, because of their ability to be rendered alternately light-absorbing and non-light absorbing by adjusting the pH of their environment, find particular utility in photographic processes employing composite photographic film units containing means for modulating environmental pH and particularly, in diffusion transfer processes of the type described in aforementioned U.S. Pat. No. 3,415,644 and in aforementioned U.S. patent applications Ser. Nos. 786,352; 43,782; and 101,968, filed Dec. 28, 1970. For convenience, the specifications of these applications and of the patent are specifically incorporated herein.

Specifically, the present invention is directed to photographic processes comprising the steps of selectively exposing a photosensitive element comprising a layer of photosensitive material to radiation actinic thereto to provide a latent image therein, applying a processing composition to provide an indicator dye containing an indole radical, a second aromatic radical and a ring closing moiety bonded to the aromatic radical and to the 2- or 3-position of the indole radical in a form capable of absorbing a predetermined wavelength range of said radiation actinic to said photosensitive material, and developing said latent image while exposing said photosensitive element non-selectively to incident actinic radiation within said predetermined wavelength range, said indicator dye being present during development in a position and quantity effective to absorb radiation within said wavelength range of incident radiation in an amount sufiicient to prevent any substantial increase in the minimum density of the image obtained by said development of said latent image.

In another embodiment, a second dye(s) is present which has a principal absorption in a second and at least partly different predetermined wavelength range and the indole dye(s) and said second dye(s) together absorb radiation over the range of 400 mm. to 700 mm.

In a further embodiment, the second dye(s) is also an indicator dye having spectral absorption characteristics reversibly alterable in response to the pH of its environment, and the indole dye(s) and second dye(s) are converted to a substantially non-light absorbing form subsequent to at least the initial stages of development of the latent image.

The photographic products provided by the present invention comprise a support layer carrying a layer of photosensitive material having associated therewith an indicator dye containing an indole radical, a second aromatic radical and a ring-closing moiety bonded to the aromatic radical and to the 2- or 3-position of the indole radical.

In another embodiment, the photographic products are photographic film units particularly adapted for production of a transfer image by diffusion transfer processes and may be constructed to include a photosensitive element containing a layer of photosensitive material and an optical filter agent of the aforementioned class of indole indicator dyes adapted, subsequent to selective exposure of the photosensitive layer to form a latent image therein, to selectively absorb incident actinic radiation without deleteriously affecting either the composition of and/or the development of the latent mage, and a diffusion transfer image-receiving element.

In a further embodiment of the present invention the photographic products are film units specifically adapted to provide a dye transfer image by color diffusion transfer processes. The photosensitive layer, e.g., a photosensitive silver halide layer will have associated therewith a compound providing as a function of development of a latent image in the associated silver halide layer, an imagewise distribution of a dye image-forming material which is soluble and diffusible in the processing composition, and an optical filter agent of the aforementioned class of indole indicator dye adapted, as a function of environmental pH to selectively effect absorption of incident actinic radiation, subsequent to selective exposure of the photosensitive layer to form the latent image there- In a preferred embodiment of the present invention, a second pH sensitive dye or dyes will be used in conjunction with the aforementioned indole indicator dye(s), which dyes together will absorb incident actinic radiation over the range of 400 mm. to 700 mm. The film unit employed will comprise a composite photosensitive element including, in sequence, a first layer or support material, two or more photosensitive silver halide layers each having associated therewith a compound providing, as a function of development of a latent image in the associated silver halide layer, an imagewise distribution of image-forming material which is soluble and diffusible in the processing composition, a layer adapted to receive image-forming material diffusing thereto, a second layer or support material and means for modulating the pH of the film unit. In combination with the composite structure, a rupturable container retaining a processing composition is fixedly positioned and extends transverse a leading edge of the composite structure whereby to effect, upon application of compressive pressure, discharge of the processing composition intermediate the image-receiving layer and the next adjacent photosensitive silver halide layer.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a photographic film unit embodying the invention;

FIGS. 2, 4 and 6 are diagrammatic enlarged crosssectional views of the film unit of FIG. 1, along section line 22, illustrating the association of elements during the three illustrated states of the performance of a diffusion transfer process, for the production of a multicolor transfer image according to the invention, the thickness of the various materials being exaggerated, and wherein FIG. 2 represents an exposure stage, FIG. 4 represents a processing stage and FIG. 6 represents a product of the process;

FIGS. 3, and 7 are diagrammatic, further enlarged cross-sectional views of the film unit of FIGS. 2, 4 and 6, along section lines 33, 55 and 77, respectively, further illustrating, in detail, the arrangement of layers comprising the photosensitive laminate during the three illustrated stages of the transfer process; and l FIGS. 8 to 18 are graphic illustrations of the spectral absorption characteristics of indicator dyes of the present invention designated hereinafter as optical filter agents A, D and F through N representing the optical transmission density, i.e., absorbance of the respective agents measured on a logarithm scale over the wavelength range of 350 nm. to 750 nm. in aqueous alkaline solution at a pH substantially above their pKa.

DETAILED DESCRIPTION OF THE INVENTIQN As noted above, it has been found in accordance with the present invention that a selectively exposed photosensitive material having a latent image therein may be processed in the presence of extraneous incident radiation actinic thereto within the shorter wavelength region of the visible spectrum by reason of the protection afforded by a particular class of indicator dyes derived from indoles. Specifically, these indicator dyes contain an indole radical, a second aromatic radical and a ring-closing moiety bonded to the aromatic radical and to the 2- or 3-position of the indole radical.

Typical of such indicator dyes are those represented by the following formula:

wherein A is an aromatic radical; Z represents the atoms necessary to complete a ring-closing moiety; R is a group selected from hydrogen, alkyl and aryl; y represents the atoms necessary to complete a ring-closing moiety; m, n and p each are integers selected from 0 and 1, provided It is l and p is 0 when m is 1 and provided n is 0 and p is 1 when m is 0.

Illustrative of indicator dyes within Formula A are those as represented by the following formula:

wherein A is an aromatic radical and Y represents the atoms necessary to complete a ring-closing moiety; and

wherein A is an aromatic radical and R is selected from hydrogen, alkyl and aryl.

As the A radical in the above formulae, any aromatic radical is suitable since the desired spectral absorption characteristics are due to the indole radical, provided the indole radical is bonded to the ring-closing moiety through the 2- or 3-position. Accordingly, the A radical may be carbocyclic aryl of the benzene or naphthalene series, preferably benzene or naphthalene containing a para substituent, such as hydroxy or amino, or it may be heterocyclic aryl containing 0, N, S, P and combinations thereof. When the A radical is heterocyclic aryl, it is preferably N-heterocyclic aryl, such as indole, e.g., indol-2-yl or indol-S-yl; pyrrole, e.g., pyrr-2-yl or pyrr-S-yl and carbazole, e.g., carbazol-3-yl. Likewise, the ringclosing moiety Z and y may be any of those commonly used in pH sensitive dyes, such as, a phenolate, carboxylate or sulfonate, and preferably is a phenolate, such as,

7 3,4-benzochromane or a carboxylate such as a phthalide or naphthalide. i

In the above formulae, the indole radical and/or second aromatic radical and/ or the ring-closing moiety may be substituted, for example, with solubilizing groups to enhance the solubility of the indicator dye in the particular processing composition employed; with immobilizing groups where it is desired to render the indicator dye substantially non-diffusible in the processing composition and with electron-withdrawing and/or hydrogen-bonding groupus as appropriate to adjust the pKa of the indicator dye for the particular processing conditions employed; and with other substituents, such as alkyl groups, which do not interfere with the photographic function of the indicator dye as an optical filter agent.

Typical substituents include branched or straight chain alkyl, such as methyl, ethyl, isopropyl, n-butyl, t-butyl, hexyl, octyl dodecyl, hexadecyl, octadecyl and eicosanyl; aryl, such as, phenyl, Z-hydroxyphenyl, 2-hydroxy-4-dodecyloxyphenyl, and naphthyl; alkaryl, such as, benzyl, phenethyl, phenylhexyl, p-octylphenyl, p-dodecylphenyl; alkoxy, such as, methoxy, ethoxy, butoxy, l-ethoxy-Z- (B-ethoxyethoxy), dodecyloxy and octadecycloxy; aryloxy, such as phenoxy, benzyloxy, naphthoxy; alkoxyalkyl, such as methoxyethyl, dodecyloxyethyl; halo such as, fluoro, bromo, and chloro; trifiuoroalkyl, such as trifluoromethyl, mono and bis-trifluoromethyl carbinol; sulfonamido; sulfamoyl; amido; acyl and its derivatives; aminomethyl; sulfonyl; sulfo; cyano; amino including monoand disubstituted amino, e.g., N-ethyl amino and N,N-dimethylamino, carboxy and hydroxy.

In addition to the above, the substituent may comprise a fused ring. For example, the indole and/or second aromatic radical may contain as a substituent, a cycloaliphatic or an aromatic ring usually having 5 or 6 members, carbocyclic or heterocyclic and substituted or unsubstituted, bonded to adjacent carbon atoms, e.g.

wherein R is, e.g., OH or COOH.

As mentioned previously, the indicator dyes described above may be used as optical filter agents in any photographic process including conventional tray processing and diffusion transfer photographic techniques. In such processes, the dye or dyes during development of a selectively exposed photosensitive material will be in a position and in a concentration effective to absorb a given level of non-selective radiation incident on and actinic to the photosensitive material. The dyes may be initially disposed in the film unit, for example, in a layer coextensive with one or both surfaces of the photosensitive layer. Where selective exposure of the photosensitive material is made through a layer containing the indicator dye, when the dyes should be in a non-light-absorbing form until the processing solution is applied. Alternately, the dyes may be initially disposed in the processing composition in their light-absorbing form, for example, in the developing bath in tray processing or in the layer of processing solution distributed between the photosensitive element and the superposed image-receiving element (or spreader sheet) in diffusion transfer processing. The particular indicator dye or dyes selected should have an absorption spectrum corresponding to the sensitivity of the photosensitive layer, so as to afford protection over the predetermined wavelength range required by the particular photosensitive material employed and should have a pKa. such that they are in their colored form, i.e., light-absorbing form at the pH at which the photographic process is performed. Most commercially useful photographic processes are performed under alkaline conditions. Diffusion transfer processes, for example, usually employ highly alkaline processing solutions having a pH in excess of 12. Though the present invention is primarily concerned with indicator dyes to be used as optical filter agents in alkaline photographic systems, dyes may be selected from Formulae I and II above for use as optical filter agents in photographic processes performed under neutral or acidic conditions.

In photographic processes where the optical filter agent is retained in a stratum through which the final image is to be viewed, the color of the indicator dye may be discharged subsequent to image formation by adjusting the pH of the system to a value at which the dye is substantially non-light absorbing in the visible spectrum. Since most photographic processes are performed at an alkaline pH, the optical filter agent generally is rendered substantially colorless by reducing the environmental pH. However, where the process is carried out at acidic or neutral pH, the color of the optical filter agent is discharged by adjusting the system to a more alkaline pH at which the indicator dye is substantially non-light absorbing. In processes where the optical filter agent is removed or separated from the layer containing the final image or retained in a layer that does not interfere with viewing of the final image, it is unnecessary to convert the indicator dye to its non-light-absorbing form, though the color may be discharged if desired.

The concentration of indicator dye is selected to provide the optical transmission density required, in combination with other layers intermediate the silver halide emulsion layer(s) and the incident radiation, to prevent nonimagewise exposure, i.e., fogging, by incident actinic light during the performance of the particular photographic process. It has been found, by interposing neutral density (carbon containing) filters over a layer of titanium dioxide, that a transmission density of approximately 6.0 from said neutral density filters was effective to prevent fogging of a diffusion transfer multicolor film unit of the type described in said US. Pat. No. 3,415,644 having a transparent support layer and an Equivalent ASA Exposure Index of approximately when processed for one minute in 10,000 foot candles of color corrected light, a light intensity approxirnvating the intensity of a noon summer sun. The transmission density required to protect such a film unit under the stated conditions may also be expressed in terms of the system transmission density of all the layers intermediate the silver halide layer(s) and the incident light; the system transmission density required to protect color film units of the aforementioned type and photographic speed has been found to be on the order of 7.0 to 7.2. Lesser levels of optical transmission density would, of course, provide eifective protection for shorter processing times, lesser light intensities and/or films having lower exposure indices. The transmission density and the indicator dye concentration necessary to provide one requisite protection from incident light may be readily determined for any photographic process by following the above described procedure or obvious modifications thereof.

Since most commercial photographic processes employ photosensitive materials sensitive to and exposable by actinic radiation throughout the visible spectrum, e.g., black-and-white panchromatic silver halide emulsions and multiplayer silver halide emulsion elements, it is preferred to use a second dye in conjunction with the indole dye that has a principal absorption in a second and at least partially different predetermined wavelength range such that the combination of dyes will afford protection from non-selective incident actinic radiation over the range of 400 to 700 mm. The second dye employed may be noncolor-changing but preferably, is also pH sensitive, i.e., has reversibly alterable Spectral absorption characteristics in response to changes in the environmental pH so that it may be rendered light-absorbing or non-light-absorbing as desired. Illustrative of such dyes are phthaleins derived from phenols, such as, thyrnol phthalein. The second dye also may be initially present in the film unit or in the processing composition as discussed above either together with or separate from the indole dye, and subsequent to processing may be removed from the film unit or retained within the film structure, provided it is in a form or position such that it does not interfere with viewing of the image produced.

As noted above, in its preferred embodiments, the present invention is concerned with composite diffusion transfer photosensitive elements including a film pack or roll wherein superposed photosensitive and image-receiving elements are maintained as a laminate after formation of the final image. Such elements include at least one transparent support to allow viewing of the final image without destroying the structural integrity of the film unit. Preferably, the support carrying the photosensitive layer(s) is opaque and the support carrying the imagereceiving layer is transparent and selective photoexposure of the photosensitive layer(s) and viewing of the final image both are effected through the latter support. The final image is viewed as a reflection print, i.e., by reflected light, provided by a reflecting agent initially disposed in the processing composition applied and maintained intermediate the image-receiving and next adjacent photosensitive layer or by a preformed layer of reflectin agent initially positioned intermediate the image-receiving and next adjacent photosensitive layer. It will be understood that a preformed reflecting layer, while it should be capable of masking the photosensitive layer( s) subsequent to image formation, should not interfere with selective photoexposure of the photosensitive material prior to processing.

When utilizing reflection-type composite film units, the indicator dye or dyes employed as the optical filter agent(s) may be positioned initially in a layer of the film unit, e.g., in a layer between the image-receiving and next adjacent photosensitive layer through which photoexposure is effected provided it is incorporated under conditions, i.e., at a pH such that it will not absorb actinic radiation intended to selectively expose the photosensitive material to form a latent image therein. For example, the optical filter agent may be in a layer coated over either the image-receiving layer or the next adjacent photosensitive layer and should remain substantially non-lightabsorbing until a processing composition is applied providing a pH at which the indicator dye is capable of being rapidly converted to its light-absorbing form to provide light protection when the film unit is removed from the camera. Rather than being initially disposed in the film unit, the indicator dye may be initially present in the processing composition applied intermediate the image-receiving and next adjacent photosensitive layer subsequent to photoexposure. The dye, when initially disposed in the processing composition, will be in its light-absorbing form.

If the indicator dye should be in its colored form at the completion of processing, it should not be present in the image-receiving layer or in any other layer where it would interfere with viewing of the transfer image through the transparent support. This result may be achieved in various ways. An indicator dye which is substantially nondiifusible in the processing composition may be initially disposed in a layer over the first photosensitive layer upon which light is incident, or a difiFusible indicator dye capable of being mordanted to or over said first photosensitive layer may be applied with the processing composition. The layer of reflecting agent, either preformed or applied as a component of the processing composition, should be positioned so as to mask the layer of indicator dye over the photosensitive layer and at the same time provide a background for viewing the final image through the transparent receiving element. Where the optical filter agent is to be hidden from view by mordanting, the indicator dye selected should preferentially mordant to the photosensitive layer and not to any of the layers intermediate the lightreflecting layer and transparent support.

By hiding the optical filter agent behind the reflecting layer, greater latitude may be achieved in the selection of the indicator dye.

In accordance with the present invention, indicator dyes are provided which possess a relatively high pKa rendering them especially useful in photographic processes, such as diffusion transfer processes, conducted at relatively high pH. Such dyes may be represented by the formula:

(III) wherein one of R and R is a hydrogen-bonding group and the other is hydrogen; B is an indol-3-yl radical; and X represents the carbon atoms necessary to complete a ring-closing moiety selected from phthalide and naphthalide.

In the above formula, any hydrogen-bonding group may be used that is capable of raising the pKa. The association of two atoms through hydrogen to form a hydrogen bond between or within molecules is well known. When hydrogen is attached to an electronegative atom, for example, 0 or N, the resultant bond is polarized. If directed toward another atom (M) with an unshared pair of electrons, the hydrogen acts as a bridge between the atoms (O-H M) due to the electrostatic attraction to both atoms between which the hydrogen proton can be transferred. In the above compounds, an intramolecular hydrogen bond is formed between the -NH- of the indole ring and an adjacent hydrogen-bonding group, i.e., a group containing a heteroatom possessing an active unshared pair of electrons, such as, 0, N, S, or halogen, e.g., E, which has a free electron pair or a negative charge in basic solution and which is capable of forming a 5-, 6- or 7-membered and preferably a 5- or 6-membered hydrogen-bonded ring with the --NH-- of the indole ring. Groups containing a free electron pair include, for example, alkoxy; acyl and its derivatives 0 JLR wherein R may be hydrogen, alkyl, aryl, alkaryl; and amido COR -CH2N wherein R and R" each may be alkyl, aryl, alkaryl. Preferably, the heteroatom in the hydrogen-bonding group has attached to it a proton which is more acidic than the proton on the NH-- of the indole and ionizes in basic solution to a negative charge. Such groups include, for example, carboxy; hydroxy; o-hydroxyphenyl; bis trifluoromethyl carbinol; sulfonamido (NH4O -R"' wherein R' may be alkyl, aryl, alkaryl) and sulfamoyl (SO NH-R"" wherein R"" may be alkyl, aryl, alkaryl). Suitable R, R, R", R and R"" substituents lnclude branched or straight chain alkyl, e.g., methyl, 

